This relates generally to imaging devices, and more particularly, to imaging devices with flash matting capabilities.
Image sensors are commonly used in electronic devices such as cellular telephones, cameras, and computers to capture images. In some situations, electronic devices are also provided with a flash and processing circuitry. The processing circuitry can be used to remove and/or replace background objects in an image with a more desirable background. For example, a user of an imaging system may wish to capture an image of a flower in front of a wall and then replace the wall in the image with an outdoor scene or other user-selected background.
One common method for removing background objects uses flash-matting operations. In a conventional flash-matting operation, a first image is captured and readout using the flash and a second image is captured and read out without using the flash. Because the flash will brighten relatively nearby objects more than it will brighten relatively distant objects, the difference in pixel values between the flash image and the no-flash image can be used to determine which image pixels in an image correspond to background objects in a scene and which correspond to foreground objects in the scene.
However, a typical flash-matting operation is subject to the restriction that no objects in the scene are moving. Because the flash image and the no-flash image are captured at different times, the moving object will appear at a different location in the flash image and the no-flash image. Pixel values associated with the moving object will be different in the flash image and the no-flash image due to the motion of the object in addition to the effect of the flash. Conventional flash-matting imaging systems can therefore misidentify moving foreground objects as background objects, thereby reducing the effectiveness of the flash-matting operations.
It would therefore be desirable to be able to provide improved imaging systems with flash-matting capabilities.